It was suggested in mid 1952 that an inert polymeric material of the proper specific gravity and particle size act as a separator for the anion and cation resin components in mixed bed ion exchange systems. The purpose of the inert layer, which has no ion exchange properties, is to act as a physical buffer and minimize cross-contamination between the anion and cation components. Suitable polymeric materials to accomplish this effect were not available until recent years when inert polymers based on crosslinked acrylic polymers were produced. These polymers typically have a carefully selected size distribution which give them a settling velocity intermediate the typical heavier cations exchange resin and typically lighter anion exchange resin. Thus in a backwash operation, for example, to separate the cation and anion layers, the inert zone will form a physical barrier between the cation and anion exchange resins. These materials were quite effective in separating the components and are available commercially at this time. These materials served their chief purpose by physically minimizing cross contaminaion of cation and anion layers. Unfortunately, the materials available as inert separators were white to light tan to brownish in color and were only slightly different in color from many typical ion exchange resins. In other words, they could not offer the operator any significant visual distinction between the anion and cation resin components. In addition, after any extended use, iron rust and other sludges begin to coat the surface of the ion exchange resin and the inert material and render any distinction between the layers practically impossible.